In the related art, there is suggested a vehicle headlamp which includes a plurality of light source units using a semiconductor light-emitting element such as an LED as a light source and which synthesizes a target light distribution pattern by overlapping a plurality of light distribution patterns formed with the light irradiated from the plurality of light source units (for example, see Japanese Patent No. 4365253 “PTL 1”).
The vehicle headlamp described in PTL 1 includes: a light focusing unit including an LED with relatively high luminance and a reflector of substantially ellipse spherical shape that forms a hot zone by focusing light from the LED with high luminance; and a diffusion unit including an LED with relatively low luminance and a diffusion optical system that forms a diffusion region by diffusing light from the LED with low luminance.
According to the vehicle headlamp described in PTL 1, it is possible to form a synthetic light distribution pattern in which a hot zone is brighter (for example, a low-beam light distribution pattern), by overlapping a hot zone formed with the light irradiated from the light focusing unit (that is, the light from the LED with relatively high luminance, which is focused by the reflector of a substantially ellipse spherical shape) and the diffusion region formed with the light irradiated from the diffusion unit (that is, the light from the LED with relatively low luminance, which is diffused by the diffusion optical system).
However, in the vehicle headlamp described in PTL 1, although an LED equal to or above a certain light-emitting size is required to secure the brightness requested in the hot zone, it may be necessary to improve the light harvesting using a reflector equal to or above a certain size in order to focus the light (light source image) from the LED equal to or above the certain light-emitting size to the hot zone.
Therefore, in the vehicle headlamp described in PTL 1, although it is possible to form a synthetic light distribution pattern in which the hot zone is brighter (for example, the low-beam light distribution pattern), there is a problem that it is not possible to miniaturize the optical system including the reflector (that is, miniaturize the headlamp). If the optical system including the reflector is miniaturized (that is, the headlamp is miniaturized), the light (light source image) from the LED equal to or above the certain light-emitting size cannot be sufficiently focused, the vehicle front side other than the hot zone is brightened too and therefore there is a problem that the brightness feeling in the distance decreases (that is, the distance visibility decreases).
The disclosed subject matter is made in view of such conditions and can be configured to provide a vehicle headlamp that can be miniaturized and that can form a synthetic light distribution pattern (for example, a low-beam light distribution pattern) in which a hot zone is brighter.